Pürofoorsed

Pürofoorsed is a term used in chemistry to describe substances that ignite spontaneously in air at or below a certain temperature. This property, known as pyrophoricity, means these materials do not require an external ignition source to combust. The ignition temperature depends on the specific substance and its surface area. Fine powders or finely divided materials tend to be more pyrophoric than their bulk counterparts due to a larger surface area exposed to oxygen.

Common examples of pyrophoric substances include certain alkali metals like sodium and potassium when exposed to air, and some organometallic compounds such as tert-butyllithium. Finely divided metals like iron, zinc, and magnesium can also be pyrophoric under specific conditions, especially when in powder form. Spontaneous combustion occurs because the substance reacts exothermically with oxygen in the air, and the heat generated is sufficient to reach its ignition temperature.

Handling pyrophoric materials requires extreme caution and specialized procedures to prevent fires. They are typically stored under an inert atmosphere, such as argon or nitrogen, or under a liquid that displaces oxygen. Specialized fire extinguishers, such as Class D extinguishers for combustible metals, are necessary for extinguishing fires involving pyrophoric substances, as water or standard ABC extinguishers can exacerbate the situation. Understanding the pyrophoric nature of a substance is crucial for safe laboratory and industrial practices.